Two Russian cosmonauts on Thursday completed a tortuous six-hour spacewalk in which they launched a tiny satellite honouring first spaceman Yuri Gagarin after initially aborting the sensitive task.

Two Russian cosmonauts on Thursday completed a tortuous six-hour spacewalk in which they launched a tiny satellite honouring first spaceman Yuri Gagarin after initially aborting the sensitive task.

The Russian Space Agency announced in a statement that the six hour 22 minute mission off the International Space Station (ISS) was "successfully completed" and that the Gagarin satellite was now spinning in space.

The spacewalk was the 35th completed by Russian cosmonauts since construction of the international orbiter began in 1998.

But few were watched as closely at home than the one undertaken by Sergei Volkov and Alexander Samokutyaev on Wednesday with the world's gaze focused on Russia's ability to pick up the mantle from the retired US shuttle programme.

Updated versions of Soviet rockets will now provide the world's only link to the ISS and space officials in Moscow wanted this mission not only to highlight their achievements but also the legacy of the world's first man in space.

The 50th anniversary of Gagarin's April 12, 1961 space shot was to have been marked by the cosmonauts' launch of a student-made mini-satellite called Kedr (Ceder) -- the call signed used during the historic mission.

But television pictures from space showed Volkov and Samokutyaev -- wearing Russian Orlan-K space suits that resembled large refrigerators -- open the hatch 20 minutes behind schedule at 1450 GMT.

The two men then spent about 30 minutes tethering themselves into place before taking their first tentative steps into space with the micro-satellite in hand.

They ended up aborting their initial attempt to launch the Kedr about an hour into the spacewalk after discovering that the little device -- weighing just 30 kilograms (66 pounds) -- only had one of its two antennas in place.

The craft was designed by Russian engineers and was supposed to carry out student experiments and emit greetings in 17 languages.

Ground control outside Moscow asked the two men where the craft's second antenna went. Cosmonaut Samokutyaev replied that he did not know and that the Kedr appeared to have come equipped that way.

"I came here three months before Sergei (Volkov) and it was already just the one antenna," Samokutyaev was quoted as saying by Interfax.

The satellite's developer later told Russian reporters that the missing antenna was actually folded inside the Kedr for safekeeping during its transport to space.